1. Field of the Invention
This invention relates to an automatic multi-point distance measuring device using a plurality of light beams projected in different directions to the object field so as to measure the distances of objects which lie in these directions with the use of a lens for receiving the light beams reflected from the objects.
2. Description of the Related Art
In the active type of distance measuring device, to allow a plurality of points in the image field to be measured in distance at once, there has been a previous proposal in Japanese Laid-Open Patent Application No. Sho 60-233610 (U.S. Pat. No. 4,748,469) where light is projected as spots to various positions in the field of view of the photographic instrument, and, by taking its reflection, a plurality of object distances are detected. This distance measuring device is constructed as shown in FIG. 9. In FIG. 9, a light projecting lens 2 and a light receiving lens 5 are made by a production technique shown in FIG. 10. That is, from three lenses 5a, 5b and 5c of the same specification, respective portions of different areas are cut out. These are then combined side by side to form a composite lens 5 having three optical axes. In FIG. 9, 1 is a light source, 6 is a light sensor, and 7 is a distance measuring circuit (see FIG. 1 of U.S. Pat. No. 4,748,469).
Another production technique of using two lenses in combination to make a light receiving lens for the active type automatic distance measuring device is known in U.S. Pat. No. 4,371,261.